The demand for efficient removal of contaminants from water supplies has increased. Because of their relatively small size, many light density contaminants (e.g., microorganisms) may often not be removed by conventional processing methods including fluid separation.
Fluid separation may include any process that captures and removes materials from a liquid stream, typically resulting in a clarified liquid having reduced contaminants and a denser stream containing removed contaminants. Further treating the denser stream in a thickening process may remove additional liquid to leave a thick, pump-able slurry mixture containing nine percent to approximately twelve percent solids by weight. Under certain conditions, a de-watering process may remove more water from the slurry mixture. The de-watering process may create a stackable but still moist mixture of approximately twelve to thirty percent solids by weight. In an extreme de-watering process, the resulting mixture may have up to forty percent solids by weight. In treating a clarified liquid, an associated clarifying process may remove suspended solid particles leaving a substantially further clarified fluid.
One example of a fluid separation technique may include a membrane filtration process. Typically, a membrane filtration process removes particles from a liquid by retaining the particles in a filter of a specific size suited for a particular application. Some examples of membrane filtration processes include microfiltration, ultrafiltration, and nanofiltration. For insoluble particles, microfiltration can be used to retain and remove these particles from a liquid. Ultrafiltration may define a purification process that serves as a primary purification filter to isolate a desired solid product of a specific size. Nanofiltration may remove contaminants as small as microscopic bacterial cyst in a final purification process.
Another example of a fluid separation technique may include centrifugal separation. A centrifuge may use centrifugal force to separate contaminants from a fluid medium by producing a denser stream containing removed contaminates and a clarified fluid stream with less contaminates. Typically, the centrifugal force is several times greater than gravity, which causes more dense contaminants to separate from the fluid medium. During separation, the fluid medium is often placed within a chamber that rotates along a symmetrical axis creating the centrifugal force in a radial direction away from the symmetrical axis. More dense contaminants suspended in the fluid medium are forced against an outer wall of the rotating chamber and may pass through openings in the chamber to an outer catchment basin. The resulting clarified fluid, which is less dense, remains near the axis of rotation and may typically be removed from the chamber via a clarified fluid outlet.
The centrifugal force that drives more dense contaminants to contact the outer walls may create a frictional force between the outer walls and the contaminants. Such frictional forces vary depending on the shape of the outer walls and, in some instances, may impede movement of contaminants towards the openings in the outer wall. As a result, some of the contaminants may remain trapped against the outer walls of the chamber without being removed from the fluid medium. Problems may also occur if the shape of the outer walls allows the fluid medium to pass out of the associated openings before contaminants are separated from the fluid.